Regeneration of scale-coated activated carbon with acid wash

Abstract

A method for regenerating scale-coated activated carbon used to treat crude sodium carbonate solutions in which the scale-coated carbon is acid washed with an aqueous solution containing from 1 to 15% by weight hydrochloric acid and from 0.5 to 3% by weight ammonium bifluoride.

What is claimed is: 
     
       1. A method for regenerating scale-coated activated carbon used to treat sodium carbonate solutions which comprises washing the scale-coated carbon with an aqueous acid wash solution containing from 1 to 15% by weight HCl and from 0.5 to 3% by weight NH 4  HF 2 , provided that the weight ratio of HCl to NH 4  HF 2  in the solution is at least 1.   
     
     
       2. The method of claim 1 wherein the acid wash solution contains from 5 to 15% by weight HCl and from 1 to 3% by weight NH 4  HF 2 . 
     
     
       3. The method of claim 1 wherein the acid wash solution contains from about 5 to 12% by weight HCl and from 1 to 2% by weight NH 4  HF 2 . 
     
     
       4. The method of claim 1 wherein the ratio of HCl to NH 4  HF 2  is about 4 to 6 parts by weight HCl to 1 part by weight NH 4  HF 2 . 
     
     
       5. The method of claim 1 wherein the acid wash solution is maintained at a temperature between 5° C. and 100° C. 
     
     
       6. The method of claim 1 wherein the acid wash solution is maintained at a temperature between 15° C. and 35° C. 
     
     
       7. The method of claim 1 which comprises washing the scale-coated carbon for a period of time sufficient to remove all traces of the whitish-appearing scale microscopically visible to a magnification of 10×. 
     
     
       8. The method of claim 1 which comprises washing the scale-coated carbon with about 1 to 125 liters of acid wash solution per kilogram of carbon. 
     
     
       9. The method of claim 1 which comprises washing the scale-coated carbon for a period of time from 15 minutes to 2 days. 
     
     
       10. The method of claim 1, wherein the carbon activity of spent, scale-coated carbon having an iodine number less than 800 is increased by at least 15%, as measured by the iodine adsorptivity. 
     
     
       11. The method of claim 1 which comprises washing the scale-coated carbon with cold water at a temperature between 5° to 20° C. prior to the acid washing. 
     
     
       12. The method of claim 1 which comprises washing the scale-coated carbon with hot water at a temperature above 85° C. prior to the acid washing. 
     
     
       13. The method of claim 1 which comprises washing the acid-washed carbon with hot water at a temperature above 85° C. to remove all traces of the acid wash solution and to regenerate the carbon adsorptivity further. 
     
     
       14. The method of claim 1 which comprises thermally regenerating the acid washed carbon with steam.